1. Field of the Invention
The present invention relates to the field of liquid crystal displaying techniques, and in particular to a direct-light backlight module and liquid crystal display device.
2. The Related Arts
Recently, the flat panel TV techniques undergo fast development and have replaced the conventional Cathode Ray Tube (CRT) TV. The liquid crystal display TV is a flat panel TV.
Because the liquid crystal panel cannot emit light, the liquid crystal display requires a backlight module to provide lighting to realize the image displaying on liquid crystal panel. The known backlight module techniques can be divided into the direct-light type and the edge-light type according to the location of the light source. FIG. 1 shows a schematic view of an embodiment of a current direct-light backlight module. As shown in FIG. 1, a direct-light backlight module includes an optical film 101, a diffuser plate 102 and a light source 103. Optical film 101 of FIG. 1 consists of three layers of films, and is disposed on top of diffuser plate 102. Diffuser plate 102 is disposed above light source 103, and located at a light mixing distance D from light source 103.
Wherein the light mixing distance D between light source 103 and diffuser plate 102 must be sufficiently long to ensure the luminance uniformity of the backlight when viewing from above optical film 101. However, this direct-light backlight module will be thicker, which is a disadvantage to the thin design of liquid crystal display. On the other hand, when mixing light distance D is reduced, the thickness of direct-light backlight module is also reduced. But, the reduction in mixing light distance will lead to the non-uniformity of luminance of the backlight module. As shown in FIG. 2, the above areas corresponding to light source 203 will be brighter, while the areas between the corresponding areas will be darker and lead to non-uniformity of luminance. The reason why the areas between the corresponding areas will be darker is that the amount of light reaching the areas is less, which is then absorbed by optical film 201 when passing through; therefore, the light emitting from those areas will be even less, thus showing darker areas.
The known solution to solve the above non-uniformity problem is to increase the number of light bars, but the cost will also be increased.